1. Field of the Invention
This invention relates to the recovery of viscous petroleum from tar sands. More particularly, the invention relates to use of steam injected into a tar sand using pumpdown completion techniques, with recovery of the petroleum by means of production wells spaced along the deviated path of the steam injection well.
2. The Prior Art
There is continuing effort to discover a commercially practical method of recovering significant quantities of petroleum from "viscous" deposits. By "viscous" is meant petroleum deposits having a viscosity on the order of 100,000 to 1,000,000 centipoise (cp) at reservoir temperatures, such as found in the Athabasca deposits.
A major problem for economic recovery from such formations is the establishment of a suitable flow path between a source of heat and means for recovering liquid products. There are numerous patents claiming methods that have been discovered to allegedly achieve this goal.
A recent patent, U.S. Pat. No. 4,037,658, issued to Donald J. Anderson, utilizes the flow of a hot fluid through a conduit, connecting two vertical wells, to fluidize the surrounding viscous petroleum. Steam is injected into one of the wells to drive the fluidized petroleum along the path of the conduit to the second well, from wich the petroleum is recovered. While the patentee uses a deviated injection well as a source of heat, he intersects the producing well to provide a continuous flow path for "heating" steam that is conducted through conduit. A second source of steam is injected into the formation, through casing perforations in the injection well, above the packer, to drive fluidized petroleum horizontally along the path of conduit into the producer well.
U.S. Pat. No. 3,960,213, issued to John H. Striegler, et al, teaches and claims a method for recovering viscous petroleum from tar sand formations utilizing a deviated steam injection well. The tar sand formation is penetrated by a horizontally deviated injection well and a plurality of production wells positioned above and along the injection well. This patent claims use of perforated, continuous liner in the injection well. A companion patent, U.S. 3,960,214, claims casing the injection well and perforations provided where it is in contact with the formation.
Other patents in this field are U.S. Pat. Nos. 3,994,340; 3,020,901; 3,986,557 and 4,007,788. A somewhat older patent in the field is U.S. Pat. No. 3,386,508 issued to W. J. Bielstein et al. However, none of these patents are directed to the possible use of pumpdown completion techniques wherein it is possible to use controlled release of steam through valve regulated side pocket mandrels.
A recognized problem, in using steam to fluidize viscous petroleum is the difficulty of establishing and maintaining communication between the injection sites and the means for recovering the fluidized petroleum. Also, there is the problem of maintaining a sufficiently high temperature in the rejection region to maintain the petroleum in a fluidized state until it can be flowed from the production well.
These and other related disadvantages have been overcome in the present invention, which is described and claimed hereinafter.
It is therefore an object of the present invention to provide a deviated, steam-injection well that will utilize through the flowline (TFL) completion to inject steam into a viscous petroleum deposit for fluidizing same.
It is a further object to provide for recovery of such fluidized viscous petroleum by use of production wells situated essentially along and above the steam injection sites.
Yet another object is to provide variable flow steam injection sites along the steam injection well tubing path.
Another object is to provide regulated steam injection sites along the steam injection well tubing path.